The present disclosure relates to fluid filtration apparatus or units of the type intended for providing fluid filtration of liquids such as water or hydraulic fluid in systems where the filtration unit is connected to discharge clean filtered fluid to the suction side or pump inlet for providing pressurized fluid to the system.
Systems of this type typically employ a filtering cartridge disposed in a fluid pressure vessel which may be of the type having a removable lid to facilitate replacement of the filtering cartridge. However, such arrangements have the disadvantage that replacement or cleaning of the cartridge requires shut down of the system and depressurization of the pressure vessel. Therefore, in order to extend the period between replacement or service, it has been desired to provide a self-cleaning mechanism for removing debris deposited on the upstream side of the filtering cartridge without the necessity of depressurizing the system and interrupting the flow of filtered fluid to the process system. Heretofore, fluid filtering systems of this type have been provided with a wiper mechanism for scraping debris from the upstream side of the filter media element and purging the debris through a drain outlet for disposal. However, such systems have been operated with a positive pressure, both at the fluid inlet to the filtering media element and at subatmospheric pressure at the filtered fluid discharge outlet.
However, in certain fluid process systems it has been desired to operate the filtering unit discharge outlet connected to the suction side of the system or the circulating pump inlet in order to increase flow through the filter media element and to provide clean fluid to the pump. In such filtration systems, with the filtrate outlet connected to subatmospheric pressure, it has not been workable, in view of the need for positive pressure, to effect the self-cleaning and purging operations. Thus, it has been desired to provide a way or means of utilizing existing fluid filtration systems of the type having an annular filter media unit cartridge in a pressurized fluid vessel and to provide for self-cleaning or wiping of the upstream side of the filter element without necessity of depressurizing the system and interrupting the flow filtered fluid through the process system with the downstream side of the filter media element maintained at subatmospheric pressures.